This invention relates to a material flow regulating device which controls the flow of an additive material into a stream of primary material as a function of the volume, flow rate, and viscosity of the primary material. The preferred embodiment is used as a fluid regulating device in conjunction with a blood scavenging apparatus for medical operations to regulate the flow of an anticoagulent such as Heparin into the scavenged blood as a function of the volume, flow rate, and viscosity of the scavenged blood flowing through a primary fluid line.
Fluid management is a critical factor in the success of major operations such as organ transplants, major orthopedic and vascular surgery, burn operations, and other severe trauma involving high blood loss medical procedures. The lack of consistent blood flow at a sufficient rate to replace the blood lost during these medical procedures can result in complications or death due to hypovolemic or hypothermic shock. Hypovolemic shock results when there is a sudden decrease in circulating blood volume and hypothermic shock often follows the recessitation efforts to counteract the hypovolemic shock. In the attempt to quickly replenish lost blood, blood volume is replaced with lower temperature blood or other fluids resulting in a drop in the patients body core temperature, thereby inducing hypothermic shock.
Equipment is available to provide rapid infusion of replacement blood to reduce the risk of hypovolemic shock which incorporate heating systems to reduce the risk of hypothermic shock during replenishment efforts. An example of this equipment is the Haemonetics R.I.S..TM. (Rapid Infusion System) manufactured by Haemonetics Surgical Products Division, Braintree, Mass. Typically, rapid infusion systems scavenge blood from an operation site by means of a vacuum device, filter the blood, and prepare the blood for infusion back into the patient. Blood which is scavenged from and reinfused into a patient has many advantages over external source blood including confirmed blood type matching and most importantly reduced risk of contracting blood diseases such as AIDS and Hepititis.
When scavenging blood, precautions must be taken to prevent the blood from coagulating. To prevent coagulation, an anti-coagulent, such as heparin is added to the scavenged blood immediately downstream from the point of intake. The addition of an anti-coagulent prevents the scavenged blood from coagulating with other materials scavenged from the operation site such as fasts, tissue, and bone fragments and permits the blood to be filtered and re-cycled.
Typically, the addition of an anti-coagulent additive is accomplished using a steady drip of the additive into the primary scavenged blood flow. However, this method has a problem of adding too much anti-coagulent into the system when the scavenged blood flows at a low rate; and not enough anti-coagulent when the scavenged blood flow is at a higher rate. The problem with too low an anti-coagulent level is that the scavenged blood coagulates before it is processed for infusion, and the problem with too high an anti-coagulent level is that the blood will not coagulate once returned to the patient. The scavenged and recycled blood cannot have too high a concentration of the anti-coagulent because the healing process which follows the operation will be impeded as it requires the natural coagulation of blood. Therefore, the prior art system for anti-coagulent introduction creates many problems.
Further, prior art systems did not provide the medical personnel in charge of monitoring anti-coagulent flow with means which positively indicate additive flow. To solve this problem a flow meter could be attached or the volume of the feed source of the additive could be manually monitored, but meters are not always available, and manual monitoring of the anti-coagulent flow is not practical in a medical trauma situation.